1. Field of the Invention
The invention relates to a miniature temperature responsive transmitter that is capable of being encapsulated within an ingestible size capsule.
2. Description of Prior Art
The body core temperature can be accurately measured in only a few locations without implanting a sensor into the body. Most commonly, a rectal thermometer is used for core temperature measurement. However, this method is inconvenient and inaccurate in many applications. The oral temperature, which is also frequently used, is a quite unreliable measure of core temperature because of variations due to breathing and to ingesting hot and cold liquids and solids. However, an ingestible pill that would enter the digestive system would provide the most accurate means of body core temperature measurement.
Various attempts have been made to produce an ingestible size temperature pill. U.S. Pat. No. 4,689,621 issued to Kleinburg discloses an ingestible size transmitter using a unique circuit having two identically biased transistors that are connected at their base, collector and emitter. U.S. Pat. No. 3,893,111 issued to John C. Cotter describes a temperature capsule to be used with larger animals to monitor their temperatures.
However, the prior art temperature capsules contain circuit designs that require a large number of components and larger batteries that results in a capsule too large to be conveniently ingested by a patient.